1. Field of the Invention
The present invention relates to an image forming apparatus and its driving method, and more particularly, to an electrophotographic type image forming apparatus and its driving method.
2. Description of the Related Art
In general, an electrophotographic type image forming apparatus is an apparatus for forming an image by charging a photoconductor with a uniform electric potential (a charging step), performing a light scanning operation on the photoconductor to form a desired electrostatic latent image (an exposing step), supplying toner to the electrostatic latent image to develop the electrostatic latent image (a developing step), transferring the developed image to a paper (a transferring step), and fusing the developed image to a paper (a fusing step).
The electrophotographic type image forming apparatus includes a charger for charging the photoconductor, such as a photoconductive drum, with a uniform electric potential, an exposure unit for scaning light modulated according to image data onto the photoconductor to form an electrostatic latent image, a developing unit for supplying toner to the electrostatic latent image to develop the electrostatic latent image, and a transferring unit for transferring the developed image to a paper. The developing unit includes a developing roller which faces the photoconductor, a supplying roller which supplies toner to the developing roller, and an agitator.
During a charging-exposing-transferring-fusing process, the photoconductive drum, the developing roller, the supplying roller, and the agitator rotate at a fixed speed. When the developing roller, the supplying roller, and the agitator rotate, friction occurs between toner particles themselves, and between the toner particles and the developing roller, the supplying roller, the agitator, and a housing of the developing unit. The friction causes abrasion of the toner itself, and damage to the toner persistently. The toner is a compound of base resin, a pigment and an internal or external additive. The internal or external additive regulates electrical or thermal characteristics of the toner. The abrasion and damage of the toner causes the internal and external additives to malfunction. In particular, the abrasion and damage of the toner may cause the external additive to be separated from the toner, whereby the external additive fails to work properly. Deterioration in characteristic of the toner causes degradation in the developing performance, resulting in increasing of toner consumption. In addition, the deterioration in characteristic of the toner causes the toner to stick to the fuser.